Conventionally known is a connector terminal into and from which a mating terminal pin is inserted and removed (see Japanese Unexamined Utility Model Application Publication No. S49-96474). Specifically, as shown in FIG. 11, the connector terminal includes an electric connector 101 to which an electric wire 105 is connected, a lower contact piece 102 extending from the electric connector 101, and two upper contact pieces 103 continuously provided with a base portion of the lower contact piece 102 and extending in the same direction as that of the lower contact piece 102. These three contact pieces (i.e., the lower contact piece 102 and the two upper contact pieces 103) are arranged at intervals from each other in a circumferential direction of the mating terminal pin to be inserted. The contact pieces 102 and 103 are elastically deformable, and elastically deformed so that a clearance between each two adjacent leading ends thereof is widened by the mating terminal pin inserted from the leading ends side into a space surrounded by the three contact pieces 102 and 103. In the connector terminal 100, the mating terminal pin is retained by an elastic restoring force of the contact pieces 102, 103 (an elastic force for returning to the initial position). At this time, the contact pieces 102 and 103 retain the mating terminal pin while the contact pieces 102 and 103 on their leading end side in an inserting direction of the mating terminal pin are partially in contact with the mating terminal pin.
Connector terminals are required to have a retaining force so that the mating terminal pin is not pulled out of the connector terminal while in use. To obtain this retaining force, the abovementioned connector terminal 100 might, for example, have a smaller clearance between the leading ends of each adjacent contact pieces 102 and 103, that is, a smaller inscribed circle (see 8 in FIG. 12) tangent to the leading ends of the three contact pieces 102 and 103. The smaller clearance between the leading ends as above causes the mating terminal pin, which is in the state of being placed in the connector terminal 100, to be firmly retained by the elastic restoring force and thus less likely to be pulled out of the connector terminal 100.
In this case, however, a great resistance is caused when the mating terminal pin is inserted into the space surrounded by the three contact pieces 102 and 103; thus, the mating terminal pin is less likely to be all the way inserted.